One of JetPack’s features is to monitor your site and inform you when it does offline, so you can quickly fix it. That monitoring cannot obviously be done from your site itself… it’s done from JetPack’s mothership, WordPress.com
It seems you only disabled and remove JetPack, but you didn’t disconnect it.
1) Re-install the plugin, properly disconnect it, and then remove it.
2) Disconnect it from your WordPress.COM dashboard
Find detailed instructions for both options here:
https://jetpack.com/support/disconnect-jetpack-sites/
If none of the two options above works for you, please follow the link at the end of the article to open a ticket with the JetPack team so they can help you with this.
So I installed plugin again, how it says Error in login.
You may be trying to log in with your own website login credentials, instead of your JetPack/WordPress.com credentials. If you’re using the correct credentials and it’s still not working, you may need to reset your password at WordPress.COM (again, not your own website password.)
Good luck!